This invention relates to a power-assisted, manually operated vehicle and more particularly to an improved power-assisted wheelchair or the like.
Various types of vehicles are provided which are designed to be operated primarily by the manual force input by the operator. Such vehicles may take the form of bicycles, watercraft, and other forms of wheeled vehicles such as wheelchairs. Frequently, the manual power for these vehicles is either augmented or replaced by a form of prime mover such as an electric motor powered by a battery. There are many instances, however, where it is desirable to maintain the manual control for the vehicle and require the input of manual force before the power assist is applied.
For example, in wheelchairs, it has been proposed to provide an arrangement wherein an electric motor assist is provided and which generates a power assist that is dependent upon the manual force input by the rider. In this way, the rider still obtains exercise and self esteem while operating the vehicle but the power assist reduces the actual force which the operator need apply. However, these type of devices shut off the power assist as soon as the manual force is discontinued. Thus, the vehicle requires considerable manual force in spite of the power assist. In addition, the operation of the vehicle no longer resembles manual operation. That is, the manual feel is removed with this type of power assist.
It is, therefore, a principal object of this invention to provide an improved power-assist arrangement for a manually-operated vehicle wherein the manual feel is retained and the operator expenditure of energy can be substantially reduced.
It is a further object of this invention to provide a power-assisted vehicle wherein the feel of operation of the vehicle still resembles that of a manually-powered vehicle although the force input requirements from the operator are substantially reduced.
When the operator applies a manual force to the vehicle for its propulsion and a power assist is switched on in response to this manual force, the operator may receive a feeling that he is no longer in control of the vehicle. That is, if the power assist comes on too fast and is too great, then the operator may feel discomfort. In addition, if the power assist is shut off rapidly when the manual force is no longer applied, then the operation of the vehicle tends to less simulate that of a manually-powered vehicle and again operator discomfort may result.
It is, therefore, a still further object of this invention to provide an improved power-assist arrangement for a vehicle wherein the power assist is tailored so as to more closely resemble manually powered operation while still providing effective and substantial assist.
With power-assisted vehicles, particularly wheelchairs, it has been generally the practice to provide a single electric motor which drives both wheels of the wheel chair. Thus, the power-assist mode is different than the normal manual mode wherein the operator may maneuver the wheelchair by applying different inputs to the individuals wheels. With a single electric motor drive, this control may be lost.
It is, therefore, a still further object of this invention to provide an improved power-assist arrangement for a wheelchair wherein each wheel is independently controlled and powered.
As is well known, many wheelchairs are constructed in such a way so that they can be collapsed or folded for storage or transport. If electric motor power assist is provided and a separate assist is provided for each wheel, the construction may be such so as to make it more difficult to achieve compact folding of the vehicle.
That is, therefore, a still further object of this invention to provide an improved power-assisted wheelchair wherein the electric motor power arrangement is oriented in such a way as to permit folding into a compact configuration.